Often an athlete in training is clocked for the time taken to cover a premeasured distance which entails a starting signal to start timing of the event and an end signal to stop timing the event. The starting signal may be an audible sound or series of sounds, such as a whistle, beep, siren or shot sound. For an end signal, a trainer may use a stop clock or a camera with a time stamp to determine the end of the event. This invention concerns a method and apparatus for training by which the athlete no longer needs a second person to clock the time taken to cover the predetermined distance thus providing maximum scheduling flexibility for the training time.
A previous method, disclosed in Provisional Application 62/178,034, for an athlete to self time a sprint was developed by the inventors of the present invention which relied on a “slap-sync” that simultaneously created a sync time base impulse for the wrist motion sensor via a slapping or mechanical sound being made, and an acoustic impulse for the smartphone app via the phone's microphone. These two simultaneous events synchronized both time bases. The run time was then determined by subtracting the start time recorded on the sensor from the stop event recorded by the video smartphone app.
It turned out that due to the two time bases being slightly different due to the tolerance of the crystal time base, the sync would drift as a function of total run time. To mitigate this drift, in ms/s, the drift was determined by a short calibration routine so the drift component of the measured time could be subtracted. This approach was acceptable but due to non-linearities in the drift, the Allen variance, the accuracy would degrade with time requiring the two time bases to be re-synced by another “slap-sync” which introduced a new run calibration burden. This was inconvenient for the user. As an object of the present invention, a new synchronization approach has been developed that relies on a single time base on the sensor only, eliminating the drift and the need for recurring re-sync via the “slap-sync” method.